Duplex blue-print paper



' Sept. 7 1926. 1,599,147

. H.-$CHMIDT ET AL DUPLEX BLUE PRINT PAPER 4 Filed Septf4. 1923 Patented Sept. 7, 1926.

UNITED ST T S PATENT OFFICE.

HENRY SCHMIDT AND WILLIAM P. KLEB, OI BICHIOND HILL, NEW YORK.

DUPLEX BLUE-PRINT PAPER.

Application filed September This invention relates to improvements in blue print paper, the main object bein to produce a duplex paper having sensitized surfaces susceptible to stripping or separation after exposure and subsequent fixing, whereby two prints are attained by a single operation.

Another object is to provide an unusually effective formula for reparing the sensltized solution, with which the paper is permeated to a suitable extent, and also for the fixing bath used to set the prints, renderi'ng them substantially ermanent.

These objects are attained by the novel use of a duplex or layered fabric, as paper, treated chemically by the process as described in detail.

In the production of paper a relatively thin light weight web or sheet is superposed on the surface of the base sheet, each having been se arately calendered and then passed toget er through other press rolls, causin them to remain in adherence until forcib y separated when dry.

This duplex paper is thentreated by applying a sensitizing solution to the thin layer, saturating the same and permitting the lower thicker layer to become surface coated.

In the drawing, Figure 1 is a plan view of a sheet of the duplex paper showing a conventional print on its face, and Figure2 is a view of the same sheet, the front layer being partially separated from the base.

T here views show clearly that the print is disclosed on the base sheet, as well as on the thinner outer sheet, thus producing two prints at one operation.

*Figure 3 is a fragmenta perspective view of the duplex paper, showing the double layersin close proximity.

Referring more in detail to the drawing The numeral 10. designates any desired design on the top layer 11 of the sensitive paper. As the top layer is peeled off, the

4, 1923. Serial at. 600,901.

design appears on the lower layer 12, as at 13, shownin Figure 2 of the drawing.

The solution for. sensitizing blue print paper is made as follows First, dissolve in five liters of hot water,-

four thousand grams of ferrous sulfate crystals, nine hundred grams citric acid and add. enough water .to make ten liters of liquid.

Second, in five liters of hot water dissolve one thousand grams of potassium ferro cyanide, fifty grams potassium bichromate and add enough water to make ten liters.

When ready to apply take five parts of the first solution, two parts of the second solution and three parts pure cold water.

The paper may be passed with the thin sheet downward throu h the'mixture or it may be applied with a rush and after drying is in condition for exposure, in the usual manner.

After exposure the paper is thoroughly washed, preferably in running water, to remove all traces of the uncombined chemicals and dried.

Thereafter the .thin sheet can be peeled or raised from the base sheet, and it will be noticed that the outside of the thin sheet presents a negative print on both sides, a similar negative appearing on the adjacent face of the lower or base sheet.

Having thus described our invention what we claim as new and desire to secure by Letters Patent, is

As a new article of manufacture, a duplex blue print paper comprising a relatively thin outer sheet saturated by a sensitizing solution, and a heavy base sheet coated on its exterior with the solution, both sh'eets being coalesced by pressure and readily separahle when in a dry condition.

In witness whereof we have signed our names to this specification.

- HENRY SCHMIDT.

WILLIAM P. KLEB. 

